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Page 14 of 44 Jung et al. Soft Sci 2024;4:15 https://dx.doi.org/10.20517/ss.2024.02

Table 5. Advantages and disadvantages of various matrices in diabetes management
Matrix Advantages Disadvantages Suitability for DM Ref.
Sweat Non-invasive, potential for Low concentration, contaminants through skin, Moderate correlation with [202,
continuous monitoring periodic activation of sweat glands blood glucose 203]
Tears Non-invasive, minimal discomfort Low concentration, hard implementation, potential Further study of the [204,
corneal injury correlation is necessary 205]
Saliva Non-invasive, easy to collect Low concentrations, large amounts of impurities Moderate correlation with [101,
blood glucose 206]
ISF Minimally invasive, good correlation Slight delay in glucose level changes compared to High correlation with blood [207]
with glucose levels blood glucose
DM: Diabetes mellitus; ISF: interstitial fluid.

Pirovano et al. introduced SwEatch, a 3D-printed wearable sensor for real-time electrolyte monitoring in
sweat, emphasizing Na and K concentrations . The band-type platform of SwEatch incorporates a dual
[210]
+
+
macro-duct for direct monitoring, comprising three replaceable components: microfluidic unit, platform
body, and fully integrated wearable platform. The microfluidic unit features a dual macro duct for
independent sample channels [Figure 4A]. Electrode fabrication involves screen printing layers on
Polyethylene terephthalate (PET) sheets, using solid contact ISEs with poly(3,4-ethylenedioxythiophene)
(PEDOT) or poly(3-octylthiophene-2,5-diyl) (POT) as conductive polymers. POT streamlines fabrication,
enhancing reproducibility through partial automation. These electrodes exhibit sensitivity and selectivity
towards sweat interferents (H , Na , K , Mg , Ca ). The 3D printed SwEatch, with a mirrored fluidic unit,
2+
2+
+
+
+
utilizes passive capillary action to bring sweat to two independent electrodes. On-body trials during cycling
reveal sodium (1.89-2.97 mM) and potassium (3.31-7.25 mM) concentration increases over a 90-minute
exercise period [Figure 4A]. Potentiometric signals are measured, digitized, and transmitted via Bluetooth,
showcasing the potential of SwEatch for real-time electrolyte monitoring during physical activity.
Zhao et al. introduced a wearable headband nanobiosensor integrating conductive threads embedded with
zinc-oxide nanowires (NWs), designed for on-body detection of sweat lactate and Na during physical
+
exercise [Figure 4B]. The biosensor incorporates signal readout and data communication circuits, enabling
precise and wireless monitoring of human sweat. With detection ranges covering clinically relevant
concentrations (0-25 mM for lactate and 0.1-100 mM for sodium) and limits of detection at 3.61 and
0.16 mM, respectively, the device demonstrated efficacy. Figure 4B illustrates on-body testing, revealing a
potential signal change attributed to electrode saturation by sweat. Stabilization between 420 and 450 s
renders it suitable for lactate and Na signal measurement. Utilizing stable signals from the lactate and Na
+
+
sensing electrodes at 450 s, sweat concentrations were determined, resulting in values of 18.4 mM for lactate
and 22.7 mM for sodium . Additionally, Wang et al. reported a wearable sweatband sensor platform
[211]
[212]
featuring an all-solid-state ISE with a gold nanodendrite (AuNDs) array electrode . This platform enables
efficient sweat collection and real-time analysis of sweat Na during indoor exercise. As outlined in the data
+
depicted in Figure 4C, the dynamic profile of real-time Na concentration during 1.5 h of indoor cycling
+
+
displayed an initial rapid upsurge in Na levels within the first 10 min, followed by stabilization and a minor
+
decline. Subsequently, after a brief period of rest and water intake, there was another increase in Na
concentration during high-intensity exercise, indicative of pronounced sweating.
Jeerapan et al. reported a study on highly stretchable textile-based biofuel cells, employing customized
[213]
stress-resistant inks through screen-printing . These bioelectronic devices, resembling socks in their
design, were crafted with nanomaterial-based inks and incorporated serpentine patterns, showcasing